When performing percussive rock drilling, a shock wave is generated by the percussive mechanism of the drilling machine. This shock wave is transmitted as an energy stress wave through the drill rod down to the drill bit. When the stress wave reaches the drill bit, its hard metal button elements are pushed against the rock with such a strong force that the rock is fractured. In order for the hard metal button elements to come into contact with unaffected rock after one strike, the drill rod is rotated by means of a rotator including a rotation motor (often hydraulically driven) and a transmission. Rock dust is continuously removed from the front side of the drill bit by flushing.
The drilling machine is mounted on a cradle, which is movable to and fro on ad feed-beam. The drilling machine and the slide are driven towards the rock along the feed-beam by means of a feed motor which can be a hydraulic cylinder or a chain feeder.
When a new drill rig is delivered to a buyer, it is set with basic settings with respect to the drilling or operating parameters of the drill rig. These parameters are i.a. pressure and hydraulic flow levels for the different components of the rig. Further, the characteristics for the operating functions of the rig which concerns how the rig will be controlled during or react to differently sensed operating conditions are set.
The basic setting of a new drill rig is normally tuned to the operating conditions that prevail in an intended area of use of the rig and possibly to the requirements of the user. If the drill rig is moved to another site with other drilling conditions or, more generally, during considerable variations of the conditions for drilling, the parameters should be adjusted to be set differently in order to adapt to these new conditions in order for the drilling to be as efficient as possible.
Adjustments of rig settings are normally carried out manually by a technician and in some cases by the rig operator, whereby a plurality of parameters affecting the percussive mechanism, the rotation motor, the feed motor etc, of the drilling machine are set.
Basic parameters that are difficult so set are:
Feed pressure; too high can result in deviating drilling direction—too low can result in wear, loosened drill string joints and ultimately drill string breakage.
Percussion pressure; too high can result in wear and breakage, increased reflexes through the drill string—too low results in reduced productivity.
Rotation speed; too high can result in wear and sometimes deviating drilling direction—too low results in wear and reduced productivity. Except for the basic parameters, there are a large number of drilling parameters that need to be set, such as, only as an example:
Feed speed and feed control levels, Too high can result in damaged equipment if the drill bit enters a cavity during drilling; Too low results in reduced productivity.
Damping pressure control levels; Too high levels will result in reduction productivity because the percussion pressure is reduced to collaring level too often; Too low will result in wear and breakage.
Flushing medium pressure; Too thigh will result in wear of the drill bit and high consumption of energy; Too low results in that the drill bit gets stuck.
A problem with manual setting of parameters is that it is very complex to correctly provide a modern drill rig with the accurate % parameter settings, since altering one parameter can affect the conditions for one or a plurality of other parameters. In particular, the feed force and the rotation torque need to be balanced to each other to sustain an efficient drilling operation. Lack of such balance because of altered rock formation conditions may more easily lead to jamming problems.
It can thus be very difficult even for a skilled technician or operator with great knowledge about the function of the system to obtain good results. Most often a trail and error method has to be performed, which can be very time-consuming.
A consequence of this is that there are often no new adjustments made at all or that the rig is set such that operation will not be as efficient as it could have been. This could lead to either increased wear and/or unnecessary ineffective operation.
As an example of the background art can be mentioned US2004/0140112 A1. This document describes an arrangement for controlling a rock drilling process, wherein a plurality of control modes can be chosen to control drilling from different criteria. As examples of control modes are mentioned: efficiency mode, quality mode, cost mode and optimizing mode.
The Aim and Most Important Features of the Invention
The aims of the present invention are to provide a method and a device wherein the draw-backs of the background art are at least reduced.
These aims are obtained in a method and a device as above, when each operating mode relates to a particular type of rock in which drilling is to be performed and that each operating mode is selectable in order to set operating settings that are adapted to the prevailing type of rock.
Hereby is achieved that the drill rig is guaranteed to be tuned and set in the direction of as much as possible, being optimized for operating in a particular type of rock. Hereby the operating parameters will be set in order to be adapted to the prevailing drilling situation.
As an example it could be mentioned that in rock of a certain hardness, where it is easy to get rock contact, it is possible to drill “aggressively”, that is with greater feed force and percussion pressure, while in other types of rock, for example in softer rock, it can be necessary to have a more dynamic control with higher feed speed and feed speed control levels, but with lower feed force.
In each mode, the settings are also tuned to each other such that the settings co-act and do not counter-act each other, which could otherwise easily be the case with manually set systems. For example, a high percussion pressure together with low feed force could be harmful to the equipment in certain conditions. I.a. such unwanted combinations can be avoided through the invention.
Said operating parameters are preferably a plurality from the group: feed motor pressure, rotation motor pressure, control levels, rotation speed, percussion pressure, feed motor flow, rotation motor flow, flushing fluid flow, damping pressure control level, feed speed control levels.
It is preferred that activation of one control mode also sets the parameter values for, activates or de-activates different drilling control functions of the rig. Hereby said drilling control functions are one or more from the group:
Boost, which means that the percussion pressure is increased or “boosted” in the event that the drill bit meets harder rock. This is preferred in case drilling is performed in soft or medium hard rock, where the rock hardness can vary considerably.
Hole flushing. More intense flushing is called for in softer rock. Is regulated from position, air flow, number of cavities.
Damping control function, where feed pressure is regulated as a function of damping pressure. This function works well in hard rock but can be directly unsuitable in soft rock.
Boosted rotation, which can be useful in soft rock but unsuitable in hard rock because of increased bit wear.
Anti-jam function.
In the case of anti-jam function, the rotation pressure to the rotation motor as a rule will be increased when the drilling machine is on its way to get stuck, since a higher torque then is required in order to rotate the drill bit.
Should the rotation pressure continue to rise to a level corresponding to a “jamming limit”, a function with anti-jamming protection could be started resulting in reverse feed of the drill slide. If the jamming will not cease within a set time, all drilling functions should be terminated.
Pressure control of feed—flow control of feed.
In an alternative drilling control function envisaged by the applicant, a combination of pressure and flow control of the feed flow to the feed motor is provided in order to provide a more gentle and more responsive control when the drilling machine is on its way to get jammed. This function could be initiated when the rotation pressure increases above a first level, which could be a set empirically determined value of the parameter indicating that the rotation torque and thereby the rotation resistance increases above values that can be considered to correspond to normal rock drilling. Since this reduces the feed flow will function be best suited for medium and soft rock.
Said operating modes are related to any from the group: soft rock, medium hard rock, hard rock. It can also be completed with further groups such as loose rock, abrasive rock, ore containing rock etc.
Through the invention, concerning different drill controlling functions for different modes, it could be prescribed: if the function is to be active, which of a plurality of function varieties that is or are to be active, which pressure and flow levels that are to be set for initiating control measures within the respective mode.
According to a preferred embodiment, one or more parameter from the group: bit size, rod size is selected. This can preferably be made manually. Hereby the system is easily adapted to drill process influencing equipment elements. Preferably one or more of the following varies as a function of bit size: flushing flow, rotation speed, feed pressure, percussion pressure, ratio feed force—rotation torque relation, starting point for initiating anti-jam function. Also preferably one or more of the following varies as a function of rod size: percussion pressure, feed motor pressure.
Skilled operators often have a feel for the performance of the drill rig which in certain aspects goes beyond what can be obtained by a control system. According to one aspect of the invention, it has been made possible to recommend adjustments of parameters within recommended ranges or from a set value.
Although there are often problems with manual adjustments, according to this aspect of the invention, it is advantageous to allow a certain freedom for skilled operators to fine tune how the rig is set. In particular it is advantageous when the system gives the opportunity for skilled operators to influence the setting of certain parameters within certain limits that can be predetermined. In one preferred embodiment, the system gives indications of recommended settings to the operator, whereby the operator has the opportunity to make certain adjustments to recommended settings, either so as to deviate with a determined maximum value from a recommended parameter value or to make adjustments within a recommended range. These recommendations are determined in an advantageous way, such that no parameters come in conflict with each other.
The corresponding advantages are obtained in a device according to the invention.
Further advantages and features of the invention will be explained in the following detailed description.